a) Field of the Invention
The invention is directed to an arrangement for protection against harmful effects of radiation and for indicating such radiation which can preferably be designed as a viewing window or as goggles and can be used for protecting the eyes from injury due to high-intensity electromagnetic radiation.
b) Background Art
Radiation protection devices, particularly for protecting the eyes from high-energy monochromatic radiation of high surface or areal density, e.g. laser radiation, are known in numerous embodiment forms. They are mostly constructed as plates or foils of transparent material and provided with flashed materials which have a spectral filtering effect which extensively prevents the penetration of the spectral range of radiation from which the eyes are to be protected, but which admits the harmless spectral range to an extent enabling observation of the events within the space endangered by radiation, particularly in the immediate vicinity of the source of radiation.
Such flashed materials on transparent carriers are often constructed as sequences of thin interference coatings or layers of material whose properties and thickness are selected in a known manner in such a way that the interference layer system has a high reflection factor (near 100%) in the spectral range of hazardous radiation, but is only relatively slightly reflective in the neighboring spectral ranges.
Construction principles of light filtering by means of the cooperation of the spectral functions of interference filters (e.g. Fabry-Perot type or multi-cavity narrow-band filters) and absorption filters are known, for example, from "Infrared Filters" by A. Borisevich, V. G. Vereshehagain, and M. A. Validov, 1971, pages 206-208. The construction principles described in this literature cause a blocking of the transmission ranges of a higher order occurring as a result of the periodicity in interference filters by means of a combination of interference filters and absorbent substrates and/or superstrata (e.g. cemented groups) having a short-pass and/or long-pass filter characteristic. The light-blocking function can be improved when supplementing this combination by additional, usually absorbent interference layer filters as blocking groups (short-passes, long-passes). For example, the Ge/ZnS long-pass blocking filters which are frequently used in the infrared range block the entire visible spectrum by means of the absorption of germanium.
Fabry-Perot type metallic-film or metal-dielectric interference filters in which the narrow-band transmission characteristic is produced by embedding a dielectric spacing layer on both sides of semi-transparent metal mirrors is known from H. A. M. Macleod, "Thin-Film Optical Filters", Adam Hilger Ltd., Bristol (1986), pages 292-308.
Further, layer systems having absorbent and nonabsorbent layers with induced transmission in which the set of problems relating to absorption are mitigated by suitably influencing the field strengths of the stationary electrical field in the locations of the absorbent layers are known from B. V. Landan, P. H. Lissberger, "Theory of Induced Transmission Filters in Terms of Concept of Equivalent Layers", JOSA 62 (1972), No. 11, pages 1258-1264.
The described layer systems for radiation protection arrangements safely protect the eyes of the operator working in the area of the radiation field or the eyes of other persons present in the immediate vicinity from harmful radiation. On the other hand, such known arrangements have severe disadvantages insofar as the user of such a protective arrangement cannot ascertain whether or not or at what time he is exposed to the threat of radiation and after leaving the hazardous radiation zone it is no longer possible to verify any exposure to radiation which might have occurred so that the causes of exposure can also not be eliminated.